Study On Flocculation Of Oleaginous Microorganisms Based On Extended Dlvo Theory

Oleaginous microbes,possessing characterizations of high productivity,unrestrained growth environment,and flexible culture patterns are broadly regarded as suitable feedstocks for producing biofuels and other various value-added products.However,biomass harvesting is one type technological obstacles to the wholesale production of biofuels from oleaginous microbes.Thus,multiple researches focused on the exploitation of high-efficient and low-cost harvesting technologies.In this study,composition of interaction energies in different experiment systems was evaluated,and the flocculation process was analyzed and optimized based on the extended DLVO(eDLVO)theory.Firstly,adsorption model between flocculants,including soluble and insoluble flocculants,and oleaginous microbes,represented by Rhodotorula glutinis and Chlorella vulgaris,was established directed by eDLVO theory,and the flocculation potential was predicted.The results demonstrated that inorganic salts modified montmorillonoid(ISMM),poly aluminium chloride(PAC)and cationic polyacrylamide(cPAM)showed higher adsorption capacity to C.vulgaris compared with R.glutinis.Besides,cPAM obtained stronger affinity to cells than PAC.Secondly,the flocculation process of C.vulgaris and R.glutinis induced by ISMM was conducted.The maximum flocculation efficiency(FE)of 98.50%for C.vulgaris and 11.83%for R.glutinis were obtained with 4 g/L and 5 g/L flocculant within the dosage scope of 1-5 g/L.The difference of FE was then thermodynamically explained by the extend DLVO theory and the FE of R.glutinis was mechanically enhanced to 90.66%with 0.06 g/L cPAM at an optimum pH of 9.After that,aimed to utilize the remainder flocculant capacity,C.vulgaris culture was added to the aggregation of R.glutinis.Fortunately,the coagulation of R.glutinis and C.vulgaris was achieved with 0.05 g/L cPAM and 5 g/L flocculant at pH 9 and the FE reached 90.15%and 91.24%,respectively.In the last part,the adsorption model between PAC,cPAM and cells was verified.Results showed that the maximum flocculation efficiencies of PAC,cPAM to C.vulgaris and R.glutinis were 98.13%,57.24%,99.84%and 99.76%,respectively.Based on this,eDLVO theory was utilized to optimize the pH values in the flocculation process,and the following conclusions were obtained.On one hand,the optimized pH value of PAC in the flocculation process was 9 both in C.vulgaris and R.glutinis cultural systems.On the other,cPAM showed high flocculation efficiency in a relatively wide range of 5-11.Besides,the flocculation efficiency of PAC to R.glutinis was improved to 99.84%by 0.2 g/L cPAM modification,and the dosage of PAC was as little as 0.4 g/L.